Linköping Electronic Conference Proceedings
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Calibration of a Chiller Modelica model with experimental data
Full text linkThe modelling and calibration of industrial chillers can bechallenging, especially when few measurements with a largeuncertainty are available. The use of an approximatecalibration model is investigated to explore its potentialin calibrating a chiller model, constructed in Modelica.Based on the results of a well-instrumented experimentalrig of a chiller at the EDF laboratory recorded over fivedays, with a varying outdoor air temperature, anapproximated steady analysis is carried out by calibratingthe Modelica model with the experimental results (mass flowrate, temperatures, pressures). The results indicate a goodmatch between the calibrated model and the experiments anda physical sensitivity in the parameters of the model,consistent with the operation of the machine (isentropicefficiency, compressor flow rate, evaporator overheatregulation). Further work can be done on the unsteadymeasurements recorded on the chiller to improve the modeland its stochastic calibration
A Dynamic Simulation Model of Outdoor Swimming Pool with Thermal Energy Storage, Boiler and Solar Thermal Collectors
Full text linkOutdoor swimming pool facilities are significant energyconsumers, primarily due to the need to maintain thermalcomfort for swimmers, as the pool is exposed to wind andoutdoor air. To address thechallenge of reducing energy consumption, effectivesimulation of the dynamical system is essential to identifyenergy-saving solutions. This paper presents acomprehensive implementation of an outdoor swimming poolsimulation model using the Modelica programming language.The simulation model also incorporates a thermal storagesystem, a boiler, and a solar thermal collector, allowing adetailed analysis of the system. In addition, an in-depthexplanation of the physical equationsgoverning the swimming pool is provided, along with themethodology used to construct theModelica model. The results show that the model allows thesimulation of the thermal behavior of an outdoor swimmingpool, including various heat losses, solar heatgains, and heat production from the boiler and solarcollectors
Selective Evaluation of RHS during Multi-Rate Simulation
Full text linkModeling across physical domains can lead to coupledsystems that operate on different time scales.Moreover, spatially discretized models can have dynamicbehavior on only a small portion of the whole system, whilethat portion might move over time.With a single rate solver like DASSL, the step size isrestricted to fast dynamics of a few states while theothers could do much larger time steps, degrading theoverall simulation speed.Recent development of the Generic Bi-rate ODE (GBODE)solver within the OpenModelica simulation environmentaddresses these models.It allows for adaptive partitioning of slow and fast statesand progresses these partitions with different time steps.However, substantial performance improvements were not yetobserved, in part because of the rigid evaluation structureof the generated code.During each small step only the derivatives of fast statesare required, but all derivatives are computed.This paper demonstrates the use of selective equationevaluation to reduce the computational cost of multi-rateintegration as shown on a scalable example of a distributedheating system.Further uses for selective evaluation during the simulationprocess are discussed and a complexity analysis is given
Status of the TransiEnt Library: Transient Simulation of Complex Integrated Energy Systems
Full text linkThe TransiEnt Library is an open-source Modelica Libraryoriginally developed at the Hamburg University ofTechnology. It is a flexible framework for modelling andanalysing the dynamic behaviour of coupled energy systemsunder current and future scenarios. With the addition ofthree new members to the TransiEnt Library consortium,namely Fraunhofer UMSICHT, Gas- und Wärme-InstitutEssen~e.V. and XRG Simulation GmbH, the TransiEnt Libraryhas expanded its portfolio of models and methods forinvestigating the challenges in energy systems. Buildingupon the previous status report, this article presents thelatest developments in the TransiEnt library, highlithingits extended capabilities to model and simulate large,complex energy systems. The recent developments include theautomatic generation of aggregated models at district andregionals levels, as well as the modelling of medium- andlow-voltage electrical distribution networks. In addition,new concepts for the representation of large-scale heatingnetworks have been developed and are presented alongsideillustrative use cases
The DLR Cables Library
Full text linkThe DLR Cables Library can be used to simulate steel cables with nonlinear stiffness such as steel wire cables with and without non-metal core or coatings. The cable itself is simulated as discrete element component, and can easily be connected to Modelica Multibody components. Additional components like winches and pulleys are included in the library. With those, complex cable systems with multiple interconnected pulleys become possible in Modelica. Two applications of the library are demonstrated, a construction crane and a cable robot used to compensate gravitation in a space robotic application
Community Updates to the DLR ThermoFluid Stream Library
Full text linkSince its inception in 2021, the user base of the DLR ThermoFluid Stream Library has steadily grown. This growth was accompanied by improved or refined models, new additions such as models for static head pressure and also new examples, especially for teaching. This paper summarizes these updates for the reader and reports on the recent developments
Study on nuclear and renewable hybrid energy system performance prediction by using Modelica
Full text linkThe production and use of electric energy is constantly evolving in the building, industrial and transportation areas [1,2]. Looking at the electric energy production sector, the market share of variable renewable energy such as wind and solar power (PV) is continuously increasing. Among the use sectors, the transportation area is encouraged to use eco-friendly fuels, and accordingly, the use rate of battery and hydrogen electric fuel vehicles is rapidly increasing. In the building area, energy efficiency is increasing due to building energy management system (BEMS) and high-insulation materials. Since 2010, researches in nuclear-renewable hybrid energy system (NRHES) have been actively conducted to maximize efficiency in electric energy production and use. The NR HES, which combines production and use, is a system that actively controls electricity production and use and surplus energy utilization [3]. In this study performance analysis is performed for the architecture depicted in the former study[3] by digital twin for securing operation efficiency of NRHES. Digital twin is built based on multi-physics system using Modelica. All components were modeled to consider electricity, heat, mechanics and environment at the same time[4,5]
Object Oriented Modeling of Single and Multi-Bed Pressure Swing Adsorption Processes using OpenModelica
Full text linkPressure Swing Adsorption has been implemented to produce pure oxygen from air. Its model is solved using the methods of finite difference and orthogonal collocation on finite elements. Discrete events of this process are modelled using state graphs. Solution to the PSA process using a single bed is presented. With two beds, it is shown that it is possible to produce oxygen continuously. All of these have been done using OpenModelica, and the code is released as open source
Analytical Treatment of Hollow Toroid Flux Tubes
Full text linkStray flux tubes around cylindrical poles are commonlymodelled starting from the results for planar flux tubesusing the circumference of the cylinder as depth. Whilethis is a tried and tested approach, we here discussanalytical expressions using the actual axisymmetricgeometry of a fraction of a hollow torus and compare theirresults to those of the accepted approach
Modelling Aquifer Thermal Energy Storage (ATES) System with Buoyancy Flow
Full text linkAquifer Thermal Energy Storages (ATES) as long-termstorages have a strong potential to address the seasonaldiscrepancy of supply and demand of thermal energy. Theoperation of high-temperature ATES (HT-ATES) and theirintegration into district heating systems are the subjectof current research projects. Buoyancy plays an importantrole in determining how HT-ATES performs. The target ofthis paper is to present a system model in Modelica thattakes these buoyancy effects into account. The validationwith experimental data and numerical simulations shows thatthe system model represents the buoyancy effects well. Asensitivity analysis underlines the importance ofoptimizing the grid structure and shows that a highresolution in the aquifer is necessary, especially in thevertical direction. Finally, a 10-year simulation shows thedeviation of the heat recovery factor, i.e. the ratio of theamount of heat extracted to the amount of heat injected,between a model with and without buoyancy effects